My employer sent out the marching orders recently like many other community pharmacies. The email said something to the effect “if you’ve got them, shoot them.”
I’m not trying to single out my employer. Other pharmacy chains started their flu shot programs for this season weeks before we did. My question today is this: are we properly serving our patients by giving flu shots in August?
First let me qualify my reservations about giving flu shots this early in the season. Certainly, vaccination rates are important. We want everyone to protect themselves. If the choice is between getting the dose early or not getting it, I’ll gladly administer the shot as soon as I can.
But I couldn’t help but wonder a couple of things. Is there compelling data against flu shot administration this early? What does the Center for Disease Control (CDC) say on the matter?
I think the information I’ve found might cause one to wonder if we are not properly serving the public by offering flu shots this early. What if there is a drop off in effectiveness after a certain period of time? When are the months that are critical to be covered?
The CDC has a nice report on the flu. It tracks data such as confirmed cases by week in previous years as well as peak monthly data. The following is a graph that looks at the peak of the flu seasons from the 1982-1983 season through the 2013-2014 season.
Peak Month of Flu Activity
1982-83 through 2013-14
“*During 2008-2009, flu activity peaked twice because of the 2009 H1N1 pandemic. Activity in the United States peaked once in in February due to seasonal influenza activity and then again in the Spring (June), with the first wave of 2009 H1N1 viruses A second, larger peak of 2009 H1N1 activity occurred in October, the peak of the 2009-2010 season.” CDC (CDC Flu Season Data Report)
As you can see above when we talk about recent flu seasons the hardest hit months are later. There’s a spike of activity starting in December but the most likely month for the most cases is February.
If we examine the last flu season in greater detail based on reported cases, you will see a similar pattern. This indicates that coverage needs to last until at least March of a given flu season for optimal protection.
Graph is courtesy of the CDC’s Weekly Surveillance Report (CDC FluView Weekly Surveillance Report)
But what about the duration of coverage for people who do get a flu shot this time of year? Is there evidence suggesting that flu shots lose effectiveness? The data to support the flu shot not lasting an entire season is not solid. The following statement was part of the CDC’s 2012-2013 Prevention and Control Recommendations from the Advisory Committee. (Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2013–2014)
“A case-control study conducted in Navarre, Spain during the 2011–12 season revealed a decline in vaccine effectiveness from 61% (95% CI = 5–84) in the first 100 days post-vaccination, to 42% (95% CI = -39–75) for days 110–119 days post-vaccination, to -35% (95% CI = -211–41) thereafter. This decline primarily affected persons aged ≥65 years, among whom effectiveness declined from 85% (95% CI = -8–98) to 24% (95% CI = -224–82) to -208 (95% CI = -1,563–43) over the same time intervals. However, most viruses isolated among infected vaccines did not match the vaccine strains.” The report concluded that more studies are needed. It also points out that mismatches between the strains covered and cases seen could account for the decline in effectiveness.
There are lots of factors that impact the spread of the flu including school calendars, weather, and sanitation. But when you have twenty plus years of data revealing late season spikes in flu cases, doesn’t the medical community need to take a closer look at the duration of vaccine protection?
The data suggests the peak time to protect yourself is later in the season. There is a much higher risk for flu cases in the February and March months than in the August to October period.
So what would I recommend to patients? Given the 14 days it takes for full protection, I’d probably tell a patient to get the shot sometime in mid-September. That way you would be fully protected at the beginning of October and be covered through the six month period ending in March.
The only qualifiers I’d include is if one was traveling sooner or if they were attending a large event where there will be lots of people in close contact. I would not want to go to something like a large concert or state fair without first protecting myself.
If someone wants to get a flu shot today, I won’t stop them. But based on the data, we should be more concerned with these late season peaks in flu activity. Whether or not those late peaks are a result of vaccine content or duration of coverage is yet to be determined.
What about you? Do you think August flu shot administration is appropriate? Should we wait longer before administering these vaccines to our patients? Or should we focus more on the overall vaccination rate?
The Redheaded Pharmacist